In the manufacture of patterned devices such as semiconductor chips and recording heads for hard drives, a crucial step is the deposition of metal with defined pattern onto a substrate. The accuracy and consistency with which this metal deposition process takes place is critical to the manufacturing yield and performance of the device. Several techniques are known for this metal deposition process, one of which is the lift-off process. In the lift-off process a photoresist pattern is defined on a substrate such that the areas where the metal is to be deposited contains no photoresist and the remaining parts of the substrate are protected by a layer of photoresist. However, in order for the photoresist to be removed after the deposition of metal a discontinuity is required in the metal film to allow for the removal of the resist by the photoresist stripper. Several lithographic processes are known to obtain the lift-off profile.
A lift-off photoresist profile is generally one that does not have a continuous perpendicular side-wall. The preferred photoresist side-wall is such that part of the substrate is protected from the deposition of metal. Typical types of lift-off profiles used in metal deposition are shown in FIG. I-III.